Neuroendocrine Tumors

What is neuroendocrine tumors?

Neuroendocrine tumors are a group of cancers that begin in neuroendocrine cells. These are special cells found throughout the body that share features of both nerve cells and hormone-producing (endocrine) cells. Neuroendocrine cells receive signals from the nervous system and respond by releasing hormones — chemical messengers that help control functions such as digestion, blood sugar, blood pressure, and airflow in the lungs. When these cells begin to grow in an uncontrolled way, they can form a neuroendocrine tumor.

Because neuroendocrine cells exist in many organs, these tumors can appear in many different places. The most common sites include the digestive tract (stomach, small intestine, appendix, colon, and rectum), the pancreas, and the lungs. Less often, they develop in the thymus, adrenal glands, or other locations. Some neuroendocrine tumors grow very slowly over many years, while others grow and spread quickly. Doctors describe this behavior using the word “grade”: low-grade tumors tend to grow slowly, and high-grade tumors tend to grow faster.

An important feature of many neuroendocrine tumors is that they can be “functioning” or “non-functioning.” A functioning tumor releases extra hormones into the bloodstream, which can cause noticeable symptoms. A non-functioning tumor does not release meaningful amounts of hormones and may grow silently for a long time before it is found.

Neuroendocrine tumors are considered uncommon compared with cancers such as breast, lung, or colon cancer, although they are being diagnosed more often than in the past, partly because imaging tests have improved. They can occur at any age but are most often found in middle-aged and older adults. Both men and women can be affected. Understanding what is neuroendocrine tumors as a condition is the first step; the sections below explain the symptoms, causes, diagnosis, and treatment in plain language.

Symptoms of neuroendocrine tumors

Neuroendocrine tumors symptoms vary widely depending on where the tumor is located, how large it is, whether it produces hormones, and whether it has spread. Many people have no symptoms at all in the early stages, and the tumor is discovered by chance during a scan or procedure done for another reason.

When symptoms do occur, they generally fall into two groups: symptoms caused by the tumor pressing on or blocking nearby structures, and symptoms caused by excess hormones released by a functioning tumor.

Symptoms related to the tumor’s size or location may include:

• Abdominal (belly) pain or discomfort that does not go away
• A change in bowel habits, such as ongoing diarrhea or constipation
• Nausea, vomiting, or a feeling of fullness after small meals
• Unexplained weight loss
• A lump that can be felt under the skin or in the abdomen
• Cough, wheezing, or coughing up blood (when the tumor is in the lungs)
• Jaundice — yellowing of the skin or eyes — if a tumor blocks the bile ducts near the pancreas
• Bleeding from the digestive tract, which may appear as dark stools

Symptoms related to hormone release (functioning tumors) may include:

• Flushing — sudden warmth and redness of the face and neck
• Frequent, watery diarrhea
• Wheezing or shortness of breath
• A rapid or irregular heartbeat
• Low blood sugar episodes (shakiness, sweating, confusion), often linked to certain pancreatic tumors
• High blood sugar or new-onset diabetes
• Severe or recurring stomach ulcers
• Skin rashes in some hormone-producing tumor types

A specific combination of flushing, diarrhea, and wheezing is known as carcinoid syndrome. It usually occurs when a hormone-producing tumor has spread to the liver, because the liver would normally break down the hormones before they reach the rest of the body. In many cases, carcinoid syndrome is a sign of more advanced disease, although this is not true for every patient.

Symptoms also tend to change with stage. Early-stage tumors are often silent or cause vague, mild complaints that are easy to mistake for common conditions such as irritable bowel syndrome. As a tumor grows or spreads, symptoms often become more persistent and more specific. Because these symptoms overlap with many everyday illnesses, neuroendocrine tumors are sometimes diagnosed years after symptoms first appear.

Causes and risk factors

In most people, the exact neuroendocrine tumors causes are not known. Like other cancers, these tumors develop when changes (mutations) occur in the DNA of neuroendocrine cells, allowing them to grow and divide without normal controls. In the majority of cases, these DNA changes happen by chance during a person’s lifetime and are not inherited.

However, some factors are known or suspected to increase the risk:

• Inherited genetic syndromes. A small proportion of neuroendocrine tumors run in families. Conditions such as multiple endocrine neoplasia type 1 (MEN1), multiple endocrine neoplasia type 2 (MEN2), von Hippel–Lindau disease, neurofibromatosis type 1, and tuberous sclerosis complex all raise the risk of developing certain neuroendocrine tumors. People with these syndromes usually need regular monitoring.
• Family history. Having a close relative with a neuroendocrine tumor may modestly increase risk, even without a named genetic syndrome.
• Age. Most neuroendocrine tumors are diagnosed in adults, with risk generally increasing with age.
• Certain chronic conditions. Long-standing conditions that affect stomach acid production, such as chronic atrophic gastritis (long-term inflammation and thinning of the stomach lining), are linked to some stomach neuroendocrine tumors.
• Smoking. Tobacco use is associated with some lung neuroendocrine tumors, particularly the faster-growing types.

It is important to understand that having a risk factor does not mean a person will develop a tumor, and many people diagnosed with neuroendocrine tumors have no identifiable risk factor at all. There is no proven way to prevent these tumors, although avoiding tobacco and attending recommended screening if you have an inherited syndrome are sensible steps.

Diagnosis

Neuroendocrine tumors diagnosis usually involves several steps, because no single test can confirm the condition on its own. Doctors combine your medical history, a physical examination, laboratory tests, imaging, and — most importantly — a tissue sample examined under a microscope.

Blood and urine tests. Certain substances made by neuroendocrine cells can be measured in blood or urine. Chromogranin A, a protein released by many neuroendocrine tumors, is a commonly used blood marker, although it can also be raised for other reasons, including some common medications. For suspected carcinoid syndrome, doctors often measure 5-HIAA (a breakdown product of the hormone serotonin) in a urine or blood sample. Hormone levels such as insulin, gastrin, or glucagon may be checked when a specific functioning pancreatic tumor is suspected.

Imaging tests. Scans help locate the tumor and show whether it has spread. These may include:

• CT (computed tomography) and MRI (magnetic resonance imaging) — detailed cross-sectional pictures of the body.
• Somatostatin receptor imaging — many neuroendocrine tumor cells carry docking sites (receptors) for a hormone called somatostatin. Special nuclear medicine scans, such as gallium-68 DOTATATE PET/CT, use a mildly radioactive tracer that attaches to these receptors, making the tumors visible. This type of scan is often very helpful for finding small tumors and hidden spread.
• Endoscopy — a thin, flexible tube with a camera used to look inside the digestive tract or airways. Endoscopic ultrasound, which combines endoscopy with ultrasound, is especially useful for tumors of the pancreas and stomach and allows the doctor to take a biopsy at the same time.

Biopsy. The definitive step in diagnosis is a biopsy — removing a small piece of the tumor so a pathologist (a doctor who studies tissue) can examine it under a microscope. The pathologist confirms that the cells are neuroendocrine, usually with special stains, and assigns a grade. Grading is typically based on how fast the cells are dividing, often measured with a marker called Ki-67. Low-grade tumors (grade 1) divide slowly, while high-grade tumors (grade 3) divide rapidly. The grade strongly influences treatment planning and outlook.

Staging. Once the diagnosis is confirmed, doctors determine the stage — how far the tumor has spread. Localized tumors are confined to the organ where they started; regional disease has reached nearby lymph nodes; and metastatic disease has spread to distant organs, most often the liver. Staging is usually completed with the imaging tests described above.

Treatment options

Neuroendocrine tumors treatment is highly individualized. The best plan depends on the tumor’s location, grade, stage, whether it produces hormones, and your overall health. Because these tumors are uncommon and behave in many different ways, care is usually coordinated by a multidisciplinary team that includes medical oncologists, surgeons, endocrinologists, radiologists, and pathologists. At Acibadem, this coordination is handled through the Medical Oncology Department, working together with the relevant surgical and imaging specialties.

Active surveillance (watchful waiting). Some very small, low-grade, slow-growing tumors — for example, certain small tumors of the stomach, rectum, or pancreas — may not need immediate treatment. Instead, your doctor may recommend regular scans and check-ups to watch for any change. This approach avoids the risks of treatment when a tumor is unlikely to cause harm in the near future.

Surgery. When a neuroendocrine tumor is localized, surgery to remove it completely is often the preferred treatment and, in many cases, can be curative. The type of operation depends on where the tumor is — it may involve removing part of the intestine, part of the pancreas, part of a lung, or the appendix. Even when the tumor has spread, surgery is sometimes used to remove as much disease as possible or to relieve symptoms such as a bowel blockage.

Somatostatin analogs. These are laboratory-made versions of the natural hormone somatostatin, given as regular injections. Medications in this group, such as octreotide and lanreotide, can reduce hormone-related symptoms like flushing and diarrhea and can also slow the growth of many low- and intermediate-grade tumors. They are often the first medication used for advanced disease.

Targeted therapy. Targeted drugs block specific pathways that tumor cells use to grow. Medicines such as everolimus and sunitinib are used for certain advanced neuroendocrine tumors, particularly those arising in the pancreas. Your doctor will consider the tumor type and previous treatments when deciding whether a targeted drug is appropriate.

Peptide receptor radionuclide therapy (PRRT). This treatment attaches a radioactive particle to a molecule that binds to somatostatin receptors on tumor cells, delivering radiation directly to the tumor while limiting exposure to healthy tissue. Lutetium-177 DOTATATE is a widely used form of PRRT for tumors that show strong receptor uptake on imaging. It is generally given as a series of infusions over several months.

Chemotherapy. Traditional chemotherapy — drugs that kill rapidly dividing cells — plays a larger role in high-grade, fast-growing neuroendocrine cancers and in some pancreatic neuroendocrine tumors. It is less commonly used for slow-growing tumors, which tend to respond less to these drugs.

Liver-directed treatments. When the disease has spread mainly to the liver, doctors may use procedures that treat the liver tumors directly. These include embolization (blocking the blood supply that feeds the tumors), ablation (destroying tumors with heat or cold), or, in selected cases, surgery on the liver itself. These approaches can control symptoms and slow disease progression in suitable patients.

Supportive and symptom-focused care. Managing hormone-related symptoms, nutrition, and quality of life is an essential part of treatment at every stage. This may include anti-diarrheal measures, dietary adjustments, and monitoring of the heart in people with long-standing carcinoid syndrome, since excess hormones can affect the heart valves over time.

Because treatment decisions involve weighing benefits, side effects, and personal preferences, it is reasonable to ask your care team to explain why a particular plan is recommended for your specific tumor type and stage.

Living with neuroendocrine tumors and outlook

The outlook for people with neuroendocrine tumors varies more than for most cancers. Many low-grade tumors grow so slowly that people live with them for many years, even when the disease has spread, while high-grade tumors can behave much more aggressively. In general, outcomes tend to be better when the tumor is low grade, found early, and removed completely with surgery. Your own doctor is the best source of information about your individual situation, because prognosis depends on details specific to your tumor.

Living with a neuroendocrine tumor often means long-term follow-up rather than a single course of treatment. Regular scans and blood tests are commonly used to monitor for recurrence or progression, sometimes for many years. If you take somatostatin analog injections, keeping to the injection schedule helps maintain symptom control.

Day-to-day, many people find it helpful to keep a symptom diary, especially if they experience flushing or diarrhea, since certain triggers — such as alcohol, stress, or particular foods — may worsen hormone-related symptoms in some individuals. A balanced diet, staying hydrated, and gentle regular activity support overall well-being during and after treatment. Emotional support also matters: living with an uncommon, long-term cancer can feel isolating, and counseling or patient support communities may help. If you have an inherited syndrome such as MEN1, your doctor may also recommend genetic counseling and screening for family members.

Frequently asked questions

What is neuroendocrine tumors in simple terms?

Neuroendocrine tumors are cancers that start in hormone-producing cells found throughout the body, most often in the digestive tract, pancreas, or lungs. Some grow slowly over many years, while others grow quickly. Some also release extra hormones that cause symptoms such as flushing or diarrhea, while others cause no hormone symptoms at all.

Are neuroendocrine tumors cancer?

Yes, neuroendocrine tumors are considered a form of cancer, although their behavior ranges widely. Low-grade tumors may grow very slowly and, when found early and removed, may never cause further problems. High-grade tumors behave more like typical aggressive cancers. Your pathology report, which includes the tumor’s grade, helps your doctor explain what to expect in your case.

Can neuroendocrine tumors be cured?

In many cases, a localized neuroendocrine tumor that is completely removed by surgery can be cured, meaning it does not come back. When the disease has spread, a complete cure is less likely, but many treatments can control the tumor and its symptoms, often for long periods. Because outcomes vary so much between tumor types, only your own care team can give you a realistic picture for your situation.

How serious are neuroendocrine tumors symptoms if I ignore them?

Symptoms such as persistent flushing, ongoing diarrhea, unexplained weight loss, or lasting abdominal pain should not be ignored, even though they often have harmless explanations. Delayed diagnosis is common with neuroendocrine tumors precisely because early symptoms are vague. Seeing a doctor early allows either reassurance or earlier treatment, which is generally associated with better outcomes.

How are neuroendocrine tumors diagnosed?

Diagnosis usually combines blood or urine tests for tumor markers and hormones, imaging such as CT, MRI, or specialized somatostatin receptor PET scans, and a biopsy, in which a small tissue sample is examined under a microscope. The biopsy confirms the diagnosis and determines the tumor’s grade, which guides treatment decisions.

What is the most common treatment for neuroendocrine tumors?

There is no single standard treatment for everyone. Surgery is often preferred when the tumor can be removed completely. For advanced or hormone-producing tumors, somatostatin analog injections are frequently the first medication used, and options such as targeted therapy, PRRT, chemotherapy, or liver-directed procedures may follow depending on how the disease behaves. Your treatment plan should be tailored to your tumor’s type, grade, and stage.

What is recovery like after surgery for a neuroendocrine tumor?

Recovery depends on the type of operation. Removing a small tumor through an endoscope may require little downtime, while major abdominal or lung surgery typically involves a hospital stay and several weeks of gradual recovery. Most people then enter a follow-up program with periodic scans and blood tests to check for any sign of recurrence. Your surgical team can describe the expected recovery for your specific procedure.

When to see a doctor

Make an appointment with a doctor if you notice persistent symptoms that could suggest a neuroendocrine tumor, especially if they last more than a few weeks or keep coming back. These include ongoing abdominal pain, repeated episodes of flushing, chronic diarrhea, unexplained weight loss, or a change in bowel habits without an obvious cause. If you have an inherited condition such as MEN1 or a strong family history of these tumors, discuss a monitoring plan with your doctor even if you feel well.

Seek urgent medical care if you experience any of the following red-flag signs:

• Vomiting blood, or passing black, tarry, or bloody stools
• Severe, sudden abdominal pain, or pain with a swollen, rigid belly
• Signs of bowel blockage: inability to pass stool or gas, with cramping pain and vomiting
• Yellowing of the skin or eyes (jaundice), especially with dark urine or fever
• Severe shortness of breath, chest pain, or coughing up blood
• Symptoms of severe low blood sugar: confusion, sweating, shaking, fainting, or seizures
• Severe dehydration from persistent diarrhea: dizziness, very little urine, rapid heartbeat
• Sudden severe flushing with a very fast heartbeat, low blood pressure, or feeling faint

These symptoms can have many causes, and having them does not mean you have a neuroendocrine tumor. However, they always deserve prompt medical evaluation so that serious conditions can be identified and treated as early as possible.